Good DVD's that are chemical stable do last 70+ year quite easily, better then most negatives do and these are tested results.
Here is a good read.
How To Choose CD/DVD Archival Media
some tips.
Do
-Handle discs by the outer edge or the center hole
-Use a non solvent-based felt-tip permanent marker to mark the label side of the disc
-Keep dirt or other foreign matter from the disc
-Store discs upright (book style) in original jewel cases that are specified for CDs and DVDs
-Return discs to their jewel cases immediately after use
-Leave discs in their spindle or jewel case to minimize the effects of environmental changes
-Remove the shrink wrap only when you are ready to record data on the disc
-Store in a cool, dry, dark environment in which the air is clean -- relative humidity should be in the range 20% - 50% (RH) and temperature should be in the range 4°C - 20°C
-Remove dirt, foreign material, fingerprints, smudges, and liquids by wiping with a clean cotton fabric in a straight line from the center of the disc toward the outer edge
-Use deionized (best), distilled or soft tap water to clean your discs. For tough problems use diluted dish detergent or rubbing alcohol. Rinse and dry thoroughly with a lint-free cloth or photo lens tissue
-Check the disc surface before recording
Do not
-Touch the surface of the disc
-Bend the disc
-Store discs horizontally for a long time (years)
-Open a recordable optical disc package if you are not ready to record
-Expose discs to extreme heat or high humidity
-Expose discs to extreme rapid temperature or humidity changes
-Expose recordable discs to prolonged sunlight or other sources of UV light
-Write or mark in the data area of the disc (area where the laser "reads")
-Clean in a circular direction around the disc.